1. Field of the Invention
This invention relates to a device for adjustment of white balance in a color video camera.
2. Description of the Prior Art
In a color video camera, the white color portion of a photographed object is put out approximately as a white color signal. Therefore, many color video cameras are provided with white balance adjustment devices. In the conventional method for adjusting the white balance, a uniformly illuminated white or gray object covers the whole visual field of the view finder and, under that condition, a white balance is obtained by carrying out gain adjustment for each color channel with an applicable adjustment device adjusted under that condition. The conventional method, however, has necessitated use of a white object. Therefore, it has sometimes been difficult to obtain a uniformly white object when shooting on location. The conventional method for adjustment of white balance, thus, has necessitated the use of a uniformly white object having a large area. Another shortcoming of the conventional method lies in that the adjustment must be carried out while watching the view finder. There is another known method in which the video camera is provided with a white colored cap in addition to a light shielding lens cap and the white cap is mounted for white balance adjustment. The white cap method, however, has necessitated mounting of the white cap every time white balance adjustment is to be carried out and removal for every picture taking operation. This method not only has made picture taking operations more intricate, but has also imposed the problem of storing the white cap. With this prior art employed for adjustment of white balance of a color video camera, particularly that of a simplified video camera which is connected to a video tape recorder and to receive its power supply from the video tape recorder in a video system, the white balance adjustment tends to be forgotten and video recording tends to be carried out without white balance adjustment. Accordingly, the prior art methods have sometimes resulted in picture taking operations with unbalanced colors.
A further shortcoming of the conventional white balance adjustment device is that the white balance is lost every time the power source turns on and off and the white balance must be readjusted every time.